The activist investor threw his weight behind Yahoo! CEO Marissa Mayer, who is feeling the heat from investors after disclosing she was rethinking a plan to return $4 billion to shareholders.

Loeb, who is Yahoo!’s largest shareholder and controls three seats on the board, is said to back Mayer’s review of how best to use the cash.

Yahoo! said in a filing on Thursday that Mayer was spearheading a strategic review of the company, including how to handle some $4 billion in proceeds from the sale of part of its stake in Chinese company Alibaba. The money had been earmarked for investors but now could go to Mayer’s war chest.

Some investors who are concerned that the money will be wasted on acquisitions pushed the stock down 5 percent yesterday to $15.15.

Still, other investors are optimistic there will be a compromise with Yahoo! using some of the money to buy back shares.